FIG. 1, relative to prior art, diagrammatically shows an embodiment of this method. According to this embodiment, the depositing of material is carried out by way of a powder spray/fuse nozzle (100) comprising 3 concentric cones delimiting between their walls tapered annular spaces that are also concentric. A laser (150) passes through the inner cone (130) through a bore centred on the axis of said cone. The laser is focused on the point (191) where the depositing (192) of material is carried out on the object (190) being manufactured. Powder (160) is sprayed in the tapered annular space between the inner surface of the outer cone (110) and the outer surface of an intermediate cone (120), while a gas is blown into the tapered annular space between the inner surface of said intermediate cone (120) and the outer surface of the inner cone (130). The centring of the cones (110, 120, 130) in relation to one another and the adjusting of the parameters result in that the powder is sprayed according to a hollow conical stream of which the apex is, ideally, confounded with the focal point (191) of the laser (150). The distance (193) between the point (191) of material deposition and the front end of the outer cone (110) is commonly about 5 mm, without this value to be considered as exhaustive or as a limitation.
The implementation of such a method requires precise knowledge of the shape of the cone of sprayed material and a perfect centring of said cone in relation to the laser beam. More particularly in the framework of manufacturing an object that requires the implementation of complex trajectories that comprise, for example, constant variations in the orientation of the stream of powder in space, requires a perfect knowledge of the length of said cone, of the position of its centre and even of the shape of this cone. These parameters are in particular generated in a numerical control machine by way of parameters referred to as correctors or tool gauges, making it possible to control the axes appropriately, so as to respect a program that defines the movements via the displacement of the point of deposition and the orientation of the spray relative to the manufactured surface. For this purpose, it is necessary to know the relative position of this point of deposition and focal point of the laser in the system of coordinates of the machine. These programming and controlling techniques, identical to those used in the framework of manufacturing by material removal, are known from prior art and no further details are provided. In the field of material removal, the tool gauge parameters are deduced directly from the measurement of the physical tool, either outside of the machine, or in the machine.
In the case of additive manufacturing, more particularly in the framework of the CLAD method, the dimensions of the spray cone are given by the parameters for implementing the method, such as the gas flow rate and the nature of the powder sprayed, or, by the adjusting of the cones of the nozzle. Therefore, it is not possible to measure a tool gauge parameter, such as the position of the axis of the spray cone in the system of coordinates of the machine and the length of the spray cone, or to adjust the shape of said spray cone without implementing the spray method.
According to a method of prior art, the position of the axis of the laser is obtained by carrying out a low-energy shot on an adhesive strip stuck on the end of the nozzle. The end of the nozzle leaves a trace on the adhesive portion, and the laser shot makes a hole in the strip. This method makes it possible to adjust the concentricity of the two marks: the hole and the trace of the nozzle, by acting on the appropriate settings of the cones of the nozzle. This is in any case an indirect measurement which has to be repeated several times in order to carry out the adjustment. The quality of the adjustment is random, and even an experienced operator cannot claim a repeatability error less than 0.5 mm. In any case, this prior art technique does not make it possible to determine the tool gauge, i.e. the length and, if needed, the shape of the spray cone.